A numerical simulation has been performed of the propagation of an action potential through cardiac tissue. The bidomain model was used to account for the effect of both tissue anisotropy and the interstitial space on current flow. A relaxation technique was used to solve the nonlinear partial differential equations. The model has been modified to predict propagation in a two- or three-- dimensional tissue, due to a point source of current. The influence of unequal anisotropy ratios of the intracellular and extracellular conductivities is being investigated. Pairs of stimulus pulses are applied to a two-dimensional sheet of tissue to create rotors and other unusual phenomena, which could prove useful as models of cardiac arrhythmias and fibrillation. The interaction of cardiac tissue with a uniform electric field was also examined.